Visual inspection of tires is widespread in the tire industry and very frequently still relies upon the dexterity of the operators responsible for detecting any visible imperfections on the surface of the tire. To this end, numerous means of assistance have been developed for handling and making visible regions that are particularly inaccessible, such as the internal part of the tire.
The function of these means is to keep the beads of the tire in the open or spaced-apart position and to set the tire in rotation, as is described by way of example in the publication U.S. Pat. No. 4,160,537.
As the processing power of computing means increases, manufacturers have now foreseen the possibility of automating these checking tasks. To this end, lighting and digital imaging means have been introduced into the internal part of the tire in order to define the image and the internal relief. This digital image is then processed by suitable computing means and compared with a reference image so as to determine any anomalies in the surface of the tire.
The invention is aimed more particularly at the means for holding and rotating the tire during the phase of acquiring the image of the internal part of the tire.
This means has to be able to keep the tire in the open position while ensuring good geometric precision. Moreover, it must allow the lighting and image acquisition means to pass through while ensuring a relative movement of said acquisition means with respect to the tire.
Means dedicated to this function have been disclosed, by way of example, in the publication US200810066532. The apparatus described comprises a plurality of pairs of hooks, or of paws, which are aligned vertically and are intended to move apart the beads and to keep the tire in the open position. These paws rotate about an axis between an engaged position and a folded back position in order to allow the introduction and removal of the tire into and from the device.
However, this type of apparatus presents two types of problem. Specifically, although the number of pairs of paws is not limited, it can be seen that the bead deforms between two successive holding paws, and this has the effect of causing waves in the shape of the lower and upper beads with respect to the plane of the bead perpendicular to the axis of the tire, and of substantially modifying the geometry of the actual tire with respect to a theoretical image. A second drawback comes from the fact that the holding paws are fixed with respect to the bead and prevent those parts of the bead on which they rest from being imaged.